S-Z stranded cables, also known as reverse oscillating lay cables, include a group of buffer tubes helically stranded about a central strength member. The S-Z stranding of buffer tubes in an optical fiber cable may take several forms. Each ‘S’ turn may be followed immediately by a reversal to a ‘Z’ stranding direction. Alternatively, there may be several helical turns between reversals. The average lay length can be defined by the distance between reversal points divided by the number of turns between reversals. The direction or lay of the tubes periodically switches at reversal points or “switchback” locations. S-Z stranding facilitates access to the tubes at the reversal points in that there is more excess tube length to access at the reversal points.
S-Z cables are typically manufactured by stranding a plurality of dielectric buffer tubes around a strength member to form a cable core. The S-Z stranded cable core can then be forwarded to a jacketing line where a polymer jacket can be extruded over the core. Before jacketing, however, the core requires some means to secure the buffer tubes in their stranded position. The most common solution is to contrahelically wrap a pair of binder threads around the stranded core. The inclusion of contrahelically wrapped binder threads add cost and complexity to cable manufacture, as well as potentially reducing manufacturing line speeds. The binders must also be removed from an accessed section of the cable jacket in order to access a buffer tube.
Use of an adhesive central member to secure the buffer tubes in place has also been proposed, although this solution also increases complexity of manufacture.